Actuator cylinder

ABSTRACT

The invention relates to an actuator cylinder, which is intended to be operated using a control valve controlled by an operating lever. The actuator cylinder includes a cylinder barrel, a piston, and a rod, which extends outside the cylinder barrel. A detector element is fitted in connection with the rod, its angle of rotation corresponding to the current position of the piston. The control valve includes a rotatably supported slide construction, to which the detector element is connected in order to rotate the slide construction to a free-circulation position, when the piston is in a position according to the operating lever. The control valve also includes connections, between which a through-flow channel is arranged. The slide construction additionally includes a component shutting off the through-flow channel.

The present invention relates to an actuator cylinder, which is intendedto be connected to a pressure-medium system and to be operated using acontrol valve controlled by an operating lever, which control valve isarranged in connection with the actuator cylinder, and which actuatorcylinder includes

-   -   a cylinder barrel and a piston sealed and arranged to move        inside it,    -   a rod attached to the piston, which rod extends outside the        cylinder barrel at one end of it,    -   a detector element fitted in connection with the rod, which        detector element is arranged to be rotatable around its        longitudinal axis, in such a way that its angle of rotation        corresponds to the current position of the piston relative to        the cylinder barrel, and    -   connections to lead the pressure medium to the piston, according        to the position of the control valve,        in which actuator cylinder the control valve includes a        rotatably supported and multi-part coaxial slide construction,        to which the detector element is connected in order to rotate        the slide construction to a free-circulation position, when the        piston is in a position according to the operating lever.

Usually, both hydraulic and pneumatic actuator cylinders are designed tobe used in such a way that the piston of the actuator cylinder movesfrom one end position to the other. In other words, the most importantaspect is the effective movement created by the actuator cylinder, itspositioning being of secondary importance. Thus, the actuator cylinderis operated using a simple control valve, which is a mechanical orelectrical direction valve. However, the operating lever of the controlvalve must be kept turned the whole time until the piston reaches thedesired position. In addition, actuator cylinders used for steering arequite small, so that even a small movement of the operating lever willmove the piston rapidly for a long distance. This makes the steeringjerky while the sudden movements can damage the structures attached tothe actuator cylinder. Further, the control valve must be installed nextto the operator, due to the small movement of the operating lever. Thisrequires hose runs between the actuator cylinder and the control valve.In addition, the position of the piston cannot be predefined when usingconventional control valves.

Particularly in steering applications, devices based on air springs orelectric motors have also been developed, in which the operating levercan be turned directly to the desired position. These devices are,however, complicated and their use in, for instance, means of watertransport demands especially watertight protection. In addition, theknown devices are slow and demand a great deal of energy.

U.S. Pat. No. 3,915,070 discloses an actuator cylinder, in which thereis also a detector element indicating the position of the piston. In thedisclosed actuator cylinder, the longitudinal movement of the piston isconverted to a rotating movement of the detector element, which showsthe position of the piston in relation to the cylinder barrel. In thiscase too, the actuator cylinder is controlled using a conventionalcontrol valve, so that, despite the detector element, when used insteering the actuator cylinder moves in jerks. In addition, it isdifficult to exploit the position data in steering, as the indicatorconnected to the detector element is located at the end of the actuatorcylinder, or at least close to it.

U.S. Pat. No. 4,475,440 discloses one kind of actuator cylinder, inconnection with which a control valve is arranged. This is a steeringbooster using particularly in vehicles. In the control valve, there is aspecial slide construction, to which the detector element is connectedwith the aid of a herringbone gear. Thus, when the piston reaches theposition determined by the steering wheel, the slide construction hascorrespondingly rotated to the neutral position, guided by the detectorelement.

The actuator cylinder referred to above is large and contains a greatmany complicated components. In addition, the control valve is anextension of the actual cylinder barrel and contains a large number ofpieces that are difficult to machine. In addition, the body of thecontrol valve has several channels that must be machined, whichcomplicates the manufacture of the actuator cylinder. Further, thedetector element has several components and it has to be steadily fittedwith a bearing to the cylinder barrel. Due to the numerous channels andcomplicated components, the flow resistance of the pressure medium ishigh. In addition, in the neutral position of the slide construction,the pressure is released on both sides of the piston. In other words,the actuator cylinder lacks a so-called holding property, so thatexternal forces can affect the position of the piston.

The invention is intended to create a new type of actuator cylinder,which can be more easily and precisely controlled than before, but theconstruction of which is simpler and more reliable in operation thanearlier. The characteristic features of this invention are stated in theaccompanying Claims. In the actuator cylinder according to theinvention, the control valve is arranged in such a way that the pistonmoves precisely to the position shown by the operating lever of thecontrol valve. In addition, the operating lever can be movedindependently of the position of the piston once the piston has finallysettled to the position shown by the operating lever. Thus, the actuatorcylinder is particularly suitable to be applied as a steering cylinder,allowing precise and smooth steering to be achieved. In addition, thecontrol valve is preferably arranged in connection with the actuatorcylinder, which further simplifies the construction of the totalinstallation. Further, the control valve is small in size but of ruggedconstruction. In addition, the new form of construction means that flowlosses are extremely small, especially when the control valve is in thefree-circulation position. The actuator cylinder is particularlysuitable for means of water transport, as operation of the control valveof the actuator cylinder is entirely mechanical, without electricalcomponents. This also reduces the actuator cylinder's need formaintenance and increases the operating reliability of the actuatorcylinder. In addition, the actuator cylinder is extremely compact, asthe cylinder barrel for part of the control valve.

In the following, the invention is examined in detail with reference tothe accompanying drawings showing one embodiment of the invention, inwhich

FIG. 1 shows a cross-section of the actuator cylinder according to theinvention,

FIG. 2 a shows a cross-section of the actuator cylinder of FIG. 1 atlevel A-A,

FIG. 2 b shows a cross-section of the actuator cylinder of FIG. 1 atlevel B-B,

FIG. 2 c shows a cross-section of the actuator cylinder of FIG. 1 atlevel C-C,

FIG. 3 a shows a cross-section of the actuator cylinder of FIG. 1 atlevel D-D,

FIG. 3 b shows a cross-section of the actuator cylinder of FIG. 1 atlevel E-E,

FIG. 3 c shows a cross-section of the actuator cylinder of FIG. 1 atlevel F-F,

FIG. 4 a shows a cross-section of the actuator cylinder of FIG. 1 atlevel A-A, when the operating lever is turned,

FIG. 4 b shows a cross-section of the actuator cylinder of FIG. 1 atlevel B-B, when the operating lever is turned,

FIG. 4 c shows a cross-section of the actuator cylinder of FIG. 1 atlevel C-C, when the operating lever is turned,

FIG. 5 shows a cross-section of the actuator cylinder according to theinvention, when the piston is between the end positions,

FIG. 6 a shows an exploded perspective view of the components of theactuator cylinder according to the invention,

FIG. 6 b shows the actuator cylinder of FIG. 6 a with the componentsassembled, and

FIG. 7 shows a partial enlargement of FIG. 6 a.

FIG. 1 shows a cross-section of the actuator cylinder according to theinvention. Differing from the figure, the actuator cylinder, hereinaftersimply the cylinder, can be installed in any position at all, asrequired in the case in question. The cylinder according to theinvention is intended for use particularly as a steering cylinder, inwhich precision and ease of operation take precedence over high power.However, despite its small size, the use of the cylinder achievesgreater power, as well as faster but more precise movement than the useof known devices. On the other hand, the power of the cylinder can beincreased simply, for example, by increasing the size and capacity ofthe cylinder.

The cylinder is connected to a pressure-medium system, which in practiceis either a pneumatic or a hydraulic system (not shown). The cylinder isoperated by means of a control valve 10, which is correspondinglycontrolled using an operating lever 11. According to the figures, thereare suitable attachment points 12 in the operating lever 11 forattaching, for example, pivots, and thus for transmitting steeringcommands, for instance from a steering wheel, to the control valve. Onetested application has been the control cylinder of the scoop of a jetski, for which the cylinder according to the invention is preeminentlysuitable. The basic components of the cylinder include a cylinder barrel13 and a piston 14 that is sealed and arranged to move inside it. InFIG. 1, the piston 14 is shown at one end position. In addition, a rod15, which extends outside the cylinder barrel 13, is attached to thepiston 14. The rod together with the piston are the parts that move inthe longitudinal direction of the cylinder, while the other componentsremain stationary. Thus, the rod is attached to the actual structure tobe moved, such as, for example, the steering arm (not shown) of theaforesaid scoop.

Both the piston 14 and its rod 15 are equipped with suitable seals 16and 17 to prevent leakage of the pressure medium. In addition, adetector element 18 is fitted in connection with the rod. The detectorelement is arranged to be rotated relative to its longitudinal axis insuch a way that the angle of rotation corresponds to the currentposition of the piston relative to the cylinder barrel. The operation ofthe detector element is described in greater detail later, as are theconnections for leading the pressure medium to the piston according tothe position of the control valve.

According to the invention, the control valve is arranged in connectionwith the cylinder. In addition, the control valve 10 includes arotatably supported, multi-component coaxial slide construction 39, towhich the detector element 18 is connected in order to rotate the slideconstruction 39, when the piston 14 is in a position corresponding tothe operating lever 11. Thus, independently of the position of the slideconstruction, the operating lever of the control valve can be turnedfreely, irrespective of the position of the piston. In addition, whenthe operating lever is turned to some position, the piston moves, untilit reaches the position defined by the operating lever. In practice, thedetector element then turns the slide construction the whole time whilethe piston moves. The piston stops, once the slide construction hasrotated to the free-circulation position. The construction in questionis not only extremely simple and reliable, but also easy to use andprecise.

In order to connect the actuator cylinder to the pressure-medium system,there are connections 24 and 25 on essentially opposite sides of thecontrol valve 10. Between the connections 24 and 25 a through-flowchannel 40 is surprisingly also arranged. The slide construction alsoincludes a component 27 shutting off the said through-flow channel 40.In the embodiment shown, the through-flow channel 40 is formed in theslide construction 29 and there are two connections 24 and 25. Thus, thethrough flow is particularly loss-free, while the position of the pistonremains unchanged when the slide construction is in the free-circulationposition. The construction is also simple and operationally reliable.

According to the figures, the control valve 10 is preferably arranged aspart of the cylinder inside the body piece 20 forming the cylinderbarrel 13. This makes the structure durable and easy to manufacture. Thetotal length of the cylinder is also kept advantageously short. Inaddition, the rotational axis of the slide construction 39 isessentially the same as that of the detector element 18, which furthersimplifies the construction of the actuator cylinder. On the other hand,the cylinder according to the invention can be formed by adding acontrol valve according to the invention to the end of a conventionalactuator cylinder (not shown). Here, the body piece has a completelysmooth surface both externally and internally, so that it requires aslittle space as possible and is easy to manufacture. In the cylindershown, there is also a support arm 21 at the end with the operatinglever 11 and a large nut 22 at the opposite end to attach the cylinderto its application, for example, a jet ski. The same reference numbersare used for components that are operationally similar.

The smooth operation of the cylinder according to the invention isachieved with the aid of a special control valve, which includes theaforementioned slide construction. Surprisingly, the operating lever 11is used to operate directly the valve body 23 of the control valve 10.In addition, the valve body 23 is also support rotatably relative to thevalve body 23, and relative to the slide 19 of the slide construction39. Thus, when the operating lever is turned, the valve body turns by acorresponding amount, while the slide remains stationary. The operationof the control valve is described in greater detail in connection withFIGS. 4 a-4 c.

FIGS. 2 a-3 c shows the control valve in the so-called free-circulationposition. The piston 14 is in the position shown by the operating lever11, so that the pressure medium flows directly from the one connection24 of the cylinder to the other, according to FIG. 2 a. The connections24 and 25 are connected to the pressure-medium system and the compressedpressure medium is fed to one connection 24 while the other connection25 is usually connection to a pressure-medium reservoir (not shown). Inthe figure, the pressure is depicted with the letter P andcorrespondingly the return flow to the tank with the letter T. Theaforesaid connections according to the invention are arranged at thesame level of the longitudinal direction of the cylinder barrel, onopposite sides of the cylinder barrel. In the free circulation position,the through flow in the control valve is then as short as possible andthe hose runs required are correspondingly short. The through-flowchannel formed in the slide construction is shown in the figure with thereference number 40.

Surprisingly, the slide 19 and the valve body 23 are arranged insideeach other and to be able to freely rotate relative to each other.Further, the valve body 23 includes two guide pieces 26 and 27 arrangedinside each other and with cooperation. In FIG. 7, the guide pieces 26and 27 are shown separated from each other. In addition, the slide 19 isarranged rotatably between the guide pieces 26 and 27 relative to boththe valve body 23 and the cylinder barrel 13 to guide the pressuremedium. With the aid of the construction in question, the control valveis made very small and reliable in operation. By arranging suitablysmall tolerances between the components, seals are made unnecessary,while the components are, however, lubricated the whole time, especiallywhen hydraulic oil is used as the pressure medium. At the same time, thecylinder barrel can be completely smooth inside, the connections beingformed mainly in the moving parts. In other words, part of the saidconnections are arranged inside the valve body. According to FIG. 7,there are channels in the guide pieces 26 and 27 that are both radialand longitudinal relative to the cylinder barrel for the pressuremedium, which channels the slide 19 is arranged to close in thefree-circulation position. Two openings 28 and 29, which are arranged atdifferent heights in the longitudinal direction of the cylinder at anangle of 90° to each other, acts as channels in the outermost guidepiece. Thus, the flow between the openings 28 and 29 depends on theposition of the slide 19. The inner guide piece 27 is correspondingly incooperation with the slide 19, to guide with its groove 30 the flow ofthe pressure medium. In practice, the guide pieces 26 and 27 areattached to each other by a pin 31, so that rotation between them isprevented. Correspondingly, the detector element 18 is attached to theslide 19 with the aid of a second pin 32 shown in FIGS. 7 and 6 a.

As the cylinder is double acting, the pressure medium must also be ledto the rod side of the piston. For this purpose the actuator cylinderincludes boreholes 33, 33′, and 33″ arranged in the wall of the cylinderbarrel 13 in the radial and longitudinal directions of the cylinderbarrel 13. In the embodiment shown, the boreholes 33, 33′, and 33″ aremade from the outer surface of the body piece 20 and then plugged. Thus,the outer surface of the body piece remains smooth, without disturbingprotrusions.

The FIGS. 4 a-4 c show the situation, in which the operating lever 11has been turned lightly counterclockwise. The slide 19 is then still inthe position according to FIG. 2 a. In other words, the piston 14 isjust beginning to start moving. According to the above, the valve body23 and its guide pieces 26 and 27 are connected to the operating lever11 and thus follow the position of the operating lever 11. In thesituation shown, the free circulation is prevented and the pressuremedium flows from the connection 25 marked with the letter P into thegap 34 of the slide 19. In the gap 34, the pressure medium flowsdownwards towards the piston 14. This is shown by the darkened area inFIG. 4b. At the bottom of the gap 34, the pressure medium is able toflow to the lower opening 29 of the outer guide piece 26 and from therethrough the borehole 35 to the intermediate ring 36. There are boreholes37 (FIG. 3 a) at the corresponding point in the intermediate ring 36,through which the pressurized pressure medium reaches the piston 14,pushing it outwards. The movement of the piston 14 stops, when thedetector element 18 has turned the slide 19 to the free-circulationposition, according to FIG. 5. The pressure medium then flows from theconnection 24 to the other directly through the gaps 34 of the slide 19and the upper opening 28 of the outer guide piece 26. When the piston 14moves in the direction described above, the pressure medium is able toflow from the rod 15 side of the piston 14 through the boreholes 33,33′, and 33″ machined in the wall of the cylinder barrel 13 to the loweropening 29 (FIG. 4 c) of the outer guide piece 26 and from there intothe slide 19. Finally, the pressure medium flows from the upper part ofthe gap 34 of the slide 19 to the connection 25 leading to the tank.When the operating lever is turned clockwise, the direction of movementof the piston changes. However, the return flow has always wider flowroutes than the pressure flow.

In practice, in the free-circulation position of the slide, theconnections leading to and from the piston are close, so that the pistonis locked into the position in question. This is also termed the holdingproperty. The shutting off takes place particularly between the guidepiece 26 and the slide 19 (FIG. 4 c). In the embodiment shown, the outerguide piece 26 on the one hand divides the flows going in differentdirections and, on the other, prevents, together with the slide, flowsto the piston in the free-circulation position. The slide 19correspondingly forms either a radial or a longitudinal channel. In thefree-circulation position, the slide 19 forms a through-flow channel 40and in the operating position a longitudinal channel 40′ between theopenings of the guide pieces. The inner guide piece 27 prevents freecirculation together with the slide 19. By means of the construction inquestion, the slide construction is simple, making the operation of thecontrol valve precise and smooth.

In practice, the operating lever and the control valve are arranged sothat the maximum movement of the operating lever corresponds at most tothe maximum rotation of the detector element. Thus, the position of thepiston always corresponds to the position of the operating lever. Inprinciple, the length of stroke of the cylinder is independent of thesaid maximum rotation. With a single type of control valve it istherefore possible to use cylinders of different sizes, simply bychanging the length of the detector element. The angle of rotation ofthe twisted slide 38 forming the detector element 18, however, affectsthe sensitivity of the control valve 10. The angle of rotation of theslide is preferably the same as the maximum movement of the operatinglever, which forms an angle α, which is 80°-130°, preferably 90°-120°,which essentially corresponds to the entire stroke of the rod of theactuator cylinder. Thus, the rotational movement of the operating levercovers the entire stroke of the cylinder. FIG. 6 a shows an explodedview of the components of the cylinder and correspondingly FIG. 6 bshows them assembled ready for installation. The slide 38 is controlledfrom the groove 39 (FIG. 3 b) formed in the piston 14.

The stroke of one tested cylinder was 200 mm and the diameter of thepiston was 50 mm. Using the cylinder in question, a force of nearly 20kN was achieved when using hydraulic oil at a pressure of 100 bar. Inthe embodiment in question, turning the operating lever, which has amaximum movement of 100°, 1° thus corresponds to a 2-mm movement of thepiston.

The cylinder according to the invention is compact and the strokeachieved with is can be easily and precisely controlled. In addition,the construction of the cylinder is simple and can be easilymanufactured and serviced. The essential aspect is the possibility toturn the operating lever independently of the position of the piston.Despite this, the piston always moves and stops at the positionindicated by the operating lever. Thus, it is possible to use specificpaths and set the operating lever to the desired position, even beforethe pressure is connected.

1. An actuator cylinder, which is intended to be connected to apressure-medium system and to be operated using a control valvecontrolled by an operating lever, which control valve is arranged inconnection with the actuator cylinder, and which actuator cylinderincludes a cylinder barrel and a piston sealed and arranged to moveinside it, a rod attached to the piston, which rod extends outside thecylinder barrel at one end of it, a detector element fitted inconnection with the rod, which detector element is arranged to berotatable around its longitudinal axis, in such a way that its angle ofrotation corresponds to the current position of the piston relative tothe cylinder barrel, and connections to lead the pressure medium to thepiston, according to the position of the control valve, in whichactuator cylinder the control valve includes a rotatably supported andmulti-part coaxial slide construction, to which the detector element isconnected in order to rotate the slide construction to afree-circulation position, when the piston is in a position according tothe operating lever, and in order to connect the actuator cylinder tothe pressure-medium system, the control valve includes connectionsbetween which a through-flow channel is arranged, and the slideconstruction additionally includes a component shutting off the saidthrough-flow channel, characterized in that, the slide construction hasa three-part structure including an outer part and a middle part and aninner part, and the outer part and the inner part are attached to eachother, and the middle part forming the said component is connected tothe detector element, while the through-flow channel goes through themiddle part.
 2. An actuator cylinder according to claim 1, characterizedin that the through-flow channel is formed in the slide construction,and that there are two connections arranged on opposite sides of thecylinder barrel at the same level in the longitudinal direction of thecylinder barrel.
 3. An actuator cylinder according to claim 1,characterized in that the control valve is arranged to form part of theactuator cylinder inside the body piece forming the cylinder barrel, andthat the axis of rotation of the slide construction is essentially thesame as that of the detector element.
 4. An actuator cylinder accordingto claim 1, characterized in that the control valve includes a valvebody connected to the operating lever, which is also rotatably supportedin relation to the cylinder barrel, and in which some of the saidconnections are arranged.
 5. An actuator cylinder according to claim 4,characterized in that the slide construction includes a slide, which isarranged inside the valve body so that both can be freely rotatedrelative to the other, to which slide the detector element is attached.6. An actuator cylinder according to claim 5, characterized in that thevalve body includes two guide pieces set inside each other and arrangedin cooperation, between which the slide is arranged rotatably inrelation to both the valve body and the cylinder barrel to guide thepressure medium.
 7. An actuator cylinder according to claim 6,characterized in that in the guide pieces there are channels that areboth radial and longitudinal to the cylinder barrel for the pressuremedium, which channels the slide is arranged to close infree-circulation position.
 8. An actuator cylinder according to claim 1,characterized in that, in order to lead the pressure medium to the rodside of the piston the actuator cylinder includes boreholes that arelongitudinal and radial to the cylinder barrel, arranged in the wall ofthe cylinder barrel.
 9. An actuator cylinder according to claim 1,characterized in that the operating lever and the control valve arearranged in such a way that the maximum movement of the operating levercorresponds at most to the maximum rotation of the detector element. 10.An actuator cylinder according to claim 1, characterized in that themaximum movement of the operating lever forms an angle α, which is80°-130°, which essentially corresponds to the entire stroke of the rodof the actuator cylinder.